'No single field mark is ever enough to be the basis for an identification.'
-David Allen Sibley
While the quotation above may be debatable in reference to some species, it very much sums up the approach one should take in making an identification between Black-backed (Motacilla (alba) lugens) and White (Motacilla alba) Wagtails. Words such as 'typically', 'generally', 'tend to', 'more', and 'less' are often employed when discussing the differences between the two forms. Both species regularly occur in Japan and can be difficult to distinguish especially those in winter or juvenal plumage. Indeed, there is debate among ornithologists as to the status of Black-backed Wagtail. The American Ornithologists' Union and the Russian checklist consider them separate species, though recent authors have lumped them together. Additionally, the common Japanese term is the same for both birds (Haku-sekirei), suggesting that they are treated as the same species in Japan. This also appears to be reflected in Japanese field guides. The confusion is magnified given the subspecies of White Wagtail one must consider in making an ID. For the present, this article will specifically focus on separation of lugens from the rest of the 'White complex' occurring in Japan, rather than on identifying the various subspecies of 'non-lugens' alba.
Range: The breeding range is the Kamchatka Peninsula, Sakhalin Island, east coast of Russia, and northern Japan. The wintering range is Japan (south of Hokkaido), Korea, eastern China, and Taiwan. They are resident in northern Honshu but are extending their range south.
General Description: Black-backed Wagtails have a thin black line through the eye and white face. The only other black/gray and white wagtail that has this line is M. alba ocularis (see below for differences). However, this line tends to be thicker in lugens than ocularis. All birds have a white or whitish forehead that typically contrasts with the gray or black crown. The bills of Black-backed Wagtails are typically longer, thicker, broader at the middle, and stronger-looking than White Wagtail. Additionally, they tend to be slightly larger (19 g vs 18 g). In general, adults tend to be brighter than immature birds, and males tend to be brighter than females.
Another distinction of lugens is that adults have more white on the flight feathers than White Wagtail. The primaries and secondaries of adults are mostly white, creating a continuous, pure white panel from the median coverts to the secondaries. In flight, the broad white inner webs of the primaries (mostly white primaries and secondaries acquired in the second prebasic molt) form a white 'window' extending more than halfway out from the base, giving the appearance of mostly white wings in flight (though first-year birds appear darker in flight). The median coverts are all white.
Males in alternate (breeding) plumage have a 'great deal of black on back' and some older birds may be entirely black-backed. The chin is usually white. Though a small percentage have black chins, the black markings will not extend across the side of the neck to the back. Females in alternate plumage are gray-backed. They tend to have more black on the nape than White Wagtail and may show some dark shading on the back. The gray back tends to be duskier than White Wagtail. Most have a white chin and upper throat (and typically have more white in this area than males). Most birds of both sexes in alternate plumage have black uppertail coverts and a black lower rump.
Males in basic (winter) plumage generally have a gray back, white throat, and black crescent-shaped band across the chest (instead of large black bib). There may be some black clouding on the back. Black feathers may be retained on lesser coverts. The rump and uppertail coverts will have more black tones than ocularis. Males tend to have more black in the crown than females. The primaries and secondaries tend to have a narrower white edge than on ocularis. Females in basic plumage, like males, generally have a gray back, white throat, and black crescent-shaped band across the chest. However, they differ in that the black crescent may be thinner than in males and mixed with white. Additionally, the black on the crown may be mixed with gray (or may appear entirely gray). There may be some black clouding on the back, though typically not as much as is found in male lugens.
Molt: The prebasic molt begins right after breeding from early July to early August, and is complete in September, usually prior to migration. A partial molt occurs in spring, from December to April on the wintering grounds. During prebasic molt, the back of the female may have a slightly more bluish color than ocularis.
First-year birds experience a partial molt in autumn. In first-year birds, the brown wings of the juvenal plumage are retained (and badly worn) in summer. Also, juvenal greater coverts are retained and appear to be tipped narrowly with white, forming white wing-bars rather than the solid white patch seen on adults. Juvenal remiges (flight feathers) are somewhat lighter and shaded less with brownish tones than ocularis. The wing pattern is similar to an adult ocularis but with less contrast.
Immature plumage: The immature male is 'virtually identical' to ocularis, though a whiter chin and paler flanks may distinguish it. The chin is typically white, though it is more likely to be black than an adult lugens. There may be some black mottling on the back. Both sexes may have extensive black on the crown. The lower rump is mostly or all black and contrasts with the gray upper rump (though the lower rump may be dusky gray in females). The median coverts of both sexes are generally all white. Unlike immature ocularis, the darker region of the greater coverts is generally paler, resulting in less contrast with the white edges. This leaves the impression of a 'white panel'. Both sexes may have a yellowish wash on the face (especially in early autumn). Additionally, both sexes may have a pale base to the lower mandible. Again, males tend to be brighter than females.
Interbreeding: While some authors report that there does not appear to be interbreeding with M. a. leucopsis or ocularis where their ranges overlap, others disagree, citing evidence for interbreeding with leucopsis. Regardless of how rare interbreeding is, it does happen, and the possibility of a hybrid should be considered when making an ID.
Subspecies occurring in Japan: Motacilla alba leucopsis, M. a. ocularis, and M. a. baicalensis.
Motacilla alba leucopsis (Houjiro Haku-sekirei): This black-backed wagtail (females have a gray back) lacks the eye stripe and should not pose much difficulty in distinguishing from Black-backed. The breeding range of leucopsis is China, the Korean Peninsula, and Japan (southwest Honshu and northern Kyushu). This is the most common form of White Wagtail occurring in Japan and has been 'extending its range northward' (Brazil, 1991).
M. a. baicalensis (Siberia Haku-sekirei): This gray-backed wagtail also primarily differs from lugens in the absence of an eye stripe.
M. a. ocularis (Taiwan Haku-sekirei): This subspecies causes the most confusion in distinguishing Black-backed from White. The breeding range of ocularis is Siberia to western Alaska and occurs in Japan as a migrant and rare winter visitor.
All ocularis are gray-backed, and the black bib on the chest extends all the way up to the base of the bill (though rare, white-chinned individuals do exist). Like lugens, adults have white or whitish foreheads that typically contrast with the gray or black crown. Ocularis have much narrower white edges to the remiges than lugens, appearing as a series of separate white lines on the folded wing. The white at the base of the primaries tends to be hidden, and the wing may appear dark in flight. The bill is typically shorter and more slender, tapered, and delicate than lugens. In alternate plumage, the uppertail coverts of both sexes are black. The upper rump of both sexes tends to be gray, while the lower rump is typically darker unlike lugens, which tends to have black or mottled black on the upper rump with a black lower rump. Additionally, the gray back will not be as dusky as a female lugens.
However, ID becomes more difficult for birds in basic plumage. To begin with, the black throat that is helpful in separating ocularis from lugens in breeding plumage is white in basic plumage (for both sexes). Confusion can be compounded by the gray backs that adult male lugens may have in basic plumage.
With ocularis, the black bib becomes a black, crescent-shaped band across the chest in basic plumage, and this band is typically narrower than that found in lugens. The band is typically thinner in females than males, and may be mixed with white. The crown will likely also contain less black in females than males. Other slight differences can be seen in the rump and uppertail coverts, which may not be as black as with lugens. Also, the median coverts tend to be less white than in lugens.
Molt: Molting may begin as early as July, but the black chin feathers of ocularis will not be replaced until August. The change is complete in September prior to migration. First-year birds experience a partial molt. A partial molt occurs in the spring, from December to April on the wintering grounds. In first-year birds, the brown wings of the juvenal plumage are retained (and badly worn) in summer. Also, the greater coverts of first-year birds are retained and appear to be tipped narrowly with white, forming white wingbars rather than the solid white patch seen on adults. Juvenal remiges are narrowly edged whitish, somewhat darker and shaded more with brownish tones than lugens. Juvenal wing pattern is similar to that of the adult, though with less contrast.
Immature plumage: The black chin and darker gray shading on the flanks of ocularis will aid in distinguishing it from the white-chinned and pale gray-flanked lugens (though it is possible that first-year birds will have white chins). Neither sex will have a black crown (though immature lugens may). First-year birds may have a dusky forehead in October and November, and this helps to separate them from lugens, which will still have a white forehead. Also, the rump of both sexes is mostly gray. Another feature of immature ocularis is that the median coverts are generally dark at the base, giving an appearance of a 'chain' between the gray scapulars and the white tips of the median coverts. In other words, there is typically a sharp contrast, giving the appearance of two white wingbars. Additionally, the greater coverts generally have darker centers, creating a toothed pattern.
General Points to Focus On:
1. A 'whiter' flight wing will suggest lugens, a darker flight wing ocularis.
2. Duskier gray parts will suggest lugens.
3. Darker upper rump suggests lugens.
4. Longer, thicker, stronger-looking bill will suggest lugens (though using this point probably requires experience).
The bird in Figure 1 provides a good illustration of the identification issues in this complex. This bird was photographed on June 10, 2003 on the Kamchatka Peninsula, and is probably not identifiable based on these images. The date of the photo and the black chin indicate alternate plumage. The gray back suggests ocularis or female lugens. The back appears to be rather dusky but the background shading and lighting make this inconclusive, though a dusky back would suggest lugens. The black chin suggests ocularis. The relatively clean white flanks and hint of gray in the greater coverts also suggest ocularis. The primaries appear to possess more black than one would expect for lugens, but the angle of the bird in this photo makes this inconclusive. Rump color is of little help, since the lower rump could be affected by shading and the upper rump cannot be seen. A black lower rump and dark upper rump would suggest lugens. Bill size/shape is difficult to go by without a comparative reference. Additionally, the date and location suggest lugens, since most birds should be on their breeding grounds by this date. In short, neither species can be ruled out. Additionally, ocularis breeds on the northern part of the Kamchatka Peninsula, so the proximity of this area makes for a greater chance of this being a hybrid bird than if it had been found in, say, central Honshu.
For further information, and a nice discussion regarding the differences between Black-backed and White Wagtail, check out Nial and Charles Moore's Birds Korea webpage.
If you believe that any of the information contained here needs refinement or if you have other comments, please contact Mike Yough (with "wagtail" in the subject box). All feedback is welcome.
My thanks to Don Roberson and the Monterey Peninsula Audubon Society for providing me access to three of the articles used in the preparation of this article. I would also like to thank fellow Kantorians, Neil Davidson and Charles Harper for their e-mail contact and support regarding this topic, as well as Yuri Artukhin, Brian Bedafort, Ingo Waschkies, and Yoshiki Watabe for their excellent photos (not all of which I was able to use). And finally, I would like to thank the amazing and wonderful Andrea Yough for taking the time to review a draft of this page and providing helpful suggestions (such as 'That's not how you spell 'juvenal').
Nisshin City, Aichi Prefecture
Brazil, M. A. (1991). The birds of Japan. Washington D. C.: Smithsonian Institution Press.
Howell, S. N. G. (1990). Identification of White and Black-backed Wagtails in alternate plumage. Western Birds, 21, 41-49.
Lee, W. S., Koo, T. H., & Park, J. Y. (2000). A field guide to the birds of Korea. Tokyo: Toyokan Publishing, Co., Ltd.
Massey, J. A., Matsui, S., Suzuki, T., Swift, E. P., Hibi, A., Ichida, N., Tsukamoto, Y., & Sonobe, K. (1982). A field guide to the birds of Japan. Tokyo: Wild Bird Society of Japan.
Morlan, J. (1981). Status and identification of forms of White Wagtail in western North America. Continental Birdlife, 2, 37-50.
Sibley, D. A. (2000). The Sibley guide to birds. New York: Alfred A. Knopf.
Sibley, D. A., & Howell, S. N. G. (1998). Identification of White and Black-backed Wagtails in basic plumage. Western Birds, 29, 180-198.
Article last updated: January 11, 2005